The present invention relates to a heat treatment machine for semiconductors. It is used in the annealing of semiconductor wafers and also in the recrystallization of amorphous or polycrystalline silicon on an insulant.
One of the essential operations in the production of integrated circuits is the doping of a semiconductor by electron acceptor or donor atoms. This operation can be carried out by ion implantation, particularly in the case of thin layer circuits. However, as ion implantation leads to the destruction of the crystalline structure of the semiconductor over a thickness of a few thousand Angstroms, it is necessary to reconstruct the crystal lattice in order to electrically activate the atoms of the implanted impurity. This reconstruction is obtained by annealing, which consists of heating the semiconductor to a high temperature, normally between 500.degree. and 1,000.degree. C.
Different annealing means are known, namely thermodiffusion furnaces or coherent light sources (lasers), as well as electron beams and graphite sheets heated by the Joule effect.
Furnace annealing has been used for many years in the semiconductor industry, but it is not really suitable for the new concepts of integrated circuits, where the main objective is to achieve a very high integration density, whilst reducing the dimensions of the component. By a diffusion mechanism furnace annealing, which requires 15 to 30 minutes at 500.degree. to 1100.degree. C., leads to a spreading out of impurities in the three dimensions of the semiconductor.
In order to retain the doping profile in the implanted areas, it is necessary to use faster annealing methods, those employing lasers or electron beams apparently being more suitable in this respect. However, the corresponding installations are complex and costly and consume a large amount of energy.